Question

A body is projected along a rough horizontal surface with a velocity $6\text{m/s}$. If the body comes to rest after travelling $9\text{m}$, then coefficient of sliding friction is $(g=10{\text{m/s}}^2)$

• A. $0.5$
• B. $0.4$
• C. $0.6$
• D. $0.2$

Answer 1

The correct option is D $0.2$

Given $u=6\text{m/s}$, $v=0$, as it comes to rest.

Now for retardation we get it by the force equation,
$f=ma$, and we know that $f=\mu mg$

So, retardation $a=\frac{\mu mg}{m}=10\mu$

Now by the equation of motion $v^2-u^2=2as$

$\Rightarrow 0=u^2-2as$, where $s=9\text{m}$
$\Rightarrow 0=\left(6^2\right)-2\left(10\mu \right)\left(9\right)$
$\therefore \mu =0.2$

Hence option D is the correct answer